Boot: Install WADs temporarily

Because the Wii NAND size is finite, mark titles that were installed
only for booting as temporary, and remove them whenever we need to
install another title (to make room). This is exactly what the
System Menu does for temporary SD card title data.

Source/Core/Core/Boot/Boot_WiiWAD.cpp

@@ -38,7 +38,7 @@ bool CBoot::BootNANDTitle(const u64 title_id)
 
 bool CBoot::Boot_WiiWAD(const DiscIO::WiiWAD& wad)
 {
-  if (!WiiUtils::InstallWAD(*IOS::HLE::GetIOS(), wad))
+  if (!WiiUtils::InstallWAD(*IOS::HLE::GetIOS(), wad, WiiUtils::InstallType::Temporary))
   {
     PanicAlertT("Cannot boot this WAD because it could not be installed to the NAND.");
     return false;

Source/Core/Core/WiiUtils.cpp

@@ -29,6 +29,7 @@
 #include "Common/NandPaths.h"
 #include "Common/StringUtil.h"
 #include "Common/Swap.h"
+#include "Common/SysConf.h"
 #include "Core/CommonTitles.h"
 #include "Core/ConfigManager.h"
 #include "Core/IOS/Device.h"
@@ -109,7 +110,7 @@ static bool ImportWAD(IOS::HLE::Kernel& ios, const DiscIO::WiiWAD& wad)
   return true;
 }
 
-bool InstallWAD(IOS::HLE::Kernel& ios, const DiscIO::WiiWAD& wad)
+bool InstallWAD(IOS::HLE::Kernel& ios, const DiscIO::WiiWAD& wad, InstallType install_type)
 {
   if (!wad.GetTMD().IsValid())
     return false;
@@ -121,20 +122,42 @@ bool InstallWAD(IOS::HLE::Kernel& ios, const DiscIO::WiiWAD& wad)
 
   // If a different version is currently installed, warn the user to make sure
   // they don't overwrite the current version by mistake.
-  if (ios.GetES()->FindInstalledTMD(wad.GetTMD().GetTitleId()).IsValid() &&
-      !AskYesNoT("A different version of this title is already installed on the NAND. "
-                 "Installing this WAD will replace it irreversibly. Continue?"))
+  const u64 title_id = wad.GetTMD().GetTitleId();
+  const IOS::ES::TMDReader installed_tmd = ios.GetES()->FindInstalledTMD(title_id);
+  const bool has_another_version =
+      installed_tmd.IsValid() && installed_tmd.GetTitleVersion() != wad.GetTMD().GetTitleVersion();
+  if (has_another_version &&
+      !AskYesNoT("A different version of this title is already installed on the NAND.\n\n"
+                 "Installed version: %u\nWAD version: %u\n\n"
+                 "Installing this WAD will replace it irreversibly. Continue?",
+                 installed_tmd.GetTitleVersion(), wad.GetTMD().GetTitleVersion()))
   {
     return false;
   }
 
-  return ImportWAD(ios, wad);
+  // Delete a previous temporary title, if it exists.
+  SysConf sysconf{Common::FROM_SESSION_ROOT};
+  SysConf::Entry* tid_entry = sysconf.GetOrAddEntry("IPL.TID", SysConf::Entry::Type::LongLong);
+  if (const u64 previous_temporary_title_id = Common::swap64(tid_entry->GetData<u64>(0)))
+    ios.GetES()->DeleteTitleContent(previous_temporary_title_id);
+
+  if (!ImportWAD(ios, wad))
+    return false;
+
+  // Keep track of the title ID so this title can be removed to make room for any future install.
+  // We use the same mechanism as the System Menu for temporary SD card title data.
+  if (!has_another_version && install_type == InstallType::Temporary)
+    tid_entry->SetData<u64>(Common::swap64(title_id));
+  else
+    tid_entry->SetData<u64>(0);
+
+  return true;
 }
 
 bool InstallWAD(const std::string& wad_path)
 {
   IOS::HLE::Kernel ios;
-  return InstallWAD(ios, DiscIO::WiiWAD{wad_path});
+  return InstallWAD(ios, DiscIO::WiiWAD{wad_path}, InstallType::Permanent);
 }
 
 // Common functionality for system updaters.

Source/Core/Core/WiiUtils.h

@@ -27,8 +27,15 @@ class Kernel;
 
 namespace WiiUtils
 {
-bool InstallWAD(IOS::HLE::Kernel& ios, const DiscIO::WiiWAD& wad);
-// Same as the above, but constructs a temporary IOS and WiiWAD instance for importing.
+enum class InstallType
+{
+  Permanent,
+  Temporary,
+};
+
+bool InstallWAD(IOS::HLE::Kernel& ios, const DiscIO::WiiWAD& wad, InstallType type);
+// Same as the above, but constructs a temporary IOS and WiiWAD instance for importing
+// and does a permanent install.
 bool InstallWAD(const std::string& wad_path);
 
 enum class UpdateResult